Seven institutions are concurrently submitting Grant Proposals to establish the Brain Tumor Cooperative Group (BTCG). That Organization will study the biology of malignant gliomas and perform clinical trials utilizing radiotherapy, chemotherapy, and interferon. Included will be studies of interstitial radiotherapy and chemotherapy delivered by the intracarotid route. A critical need for such a cooperative effort is 1) a consistent centralized pathology review of histologic diagnoses and 2) a postmortem assessment of treatments effects on the neoplasms and surrounding brain. Accordingly, histologic slides of surgical specimens from all patients will be reviewed in accord with published criteria to determine patient eligibility for BTCG Clinical Trials and the appropriate stratification for subsequent statistical analyses of survivals. Secondly, the effects of therapy on the neoplasm will be investigated by a detailed neuropathologic study of selected brains using whole brain sections and multiple labeled blocks. The findings will be correlated with clinical history, CT scans, and details of specific therapies. Issues of particular importance include a) the morphologic effects of recent therapies such as interstitial radiation, intracarotid BCNU, and interferon on malignant gliomas and b) the pathologic consequences on normal brain of new therapies for malignant gliomas or modifications of existing modalities that deliver drugs or radiation in high focal concentrations.